The invention relates to sulfur-curable, carbon black reinforced natural rubber compounds containing zinc dimethacrylate. More particularly, the invention relates to sulfur-curable, carbon black reinforced natural rubber compounds in which the cured and uncured properties are improved by the addition thereto of small amonts of a zinc dimethacrylate having a specified surface area.
U.S. Pat. No. 4,191,671 relates to abrasion resistant rubber compositions containing diene elastomers such as natural rubber, homopolymers of conjugated dienes and copolymers of conjugated dienes and vinyl aromatic hydrocarbons; an .alpha.,.beta.-ethylenically unsaturated carboxylic acid such as acrylic and methacrylic acid; a divalent metal compound such as zinc, magnesium, calcium or cobalt compound and an organic peroxide. The patent discloses that the rubber composition may also contain an unpolymerizable carboxylic acid (i.e., a saturated acid), an amine compound, carbon black and conventional fillers such as silicas, silicates and quinone dioximes.
U.S. Pat. No. 4,192,790 relates to filled elastomeric compositions having reduced viscosity in the compounded state which contain natural rubber or various synthetic polymers; an inorganic particulate filler such as a silica, a silicate or calcium carbonate and a metal salt of a monoethylenically unsaturated carboxylic acid, especially particulate, finely divided basic zinc methacrylate. The patent states that other methacrylate salts of interest include neutral (normal) zinc salt, sodium salt, basic salt of calcium, magnesium, lead, etc. The patent additionally discloses that the compositions may optionally contain compounding ingredients such as carbon black, zinc oxide, calcium stearate, peroxide curing systems or sulfur curing systems.
British Pat. No. 2,042,533 relates to crosslinked cellular elastomers comprising the reaction product of a natural rubber and/or one or more synthetic rubbers, a cross-linking agent and a monomeric metallic salt of an ethylenically-unsaturated carboxylic acid. The only cross-linking agents specifically disclosed in the reference are peroxides. Monomeric metallic salts which are disclosed include zinc dimethacrylate, zinc diacrylate, a mixture of these two or basic zinc methacrylate with basic zinc methacrylate being preferred due to its greater reproducibility. The reference further indicates that the composition may further contain other additives including fillers such as carbon black or titanium dioxide, cross-linking rate controlling agents, antioxidants and processing aids.